The Louvre is the world's largest museum and one of the world's greatest art collections in the world. The palace stretches for about half mile between the Seine and rue de Rivoli. It was originally a fortress built by Philippe-Auguste in the 13th century. 300 years later Francois I replaced it with a Renaissance style building. Many French kings continued to add to the construction and improve it. Some of the kings used it as their residence before the court moved to Versaille. Louvre was first opened to the public in 1793 and has been used as a museum ever since. The latest addition to the building is the glass pyramid (also a museum entrance) that sits in the courtyard which was designed by I. M. Pei. The pyramid was unveiled in 1989.